1. Field of the Invention
The present invention relates to a heat-transfer recording medium which permits the recording of two colors by the utilization of differences in heating temperatures.
2. The Prior Art
In accordance with the heat-transfer recording process, a thermal recording medium coated with an ink which melts or sublimates upon heating is selectively heated according to an information pattern, and the thus melted or sublimated ink is transferred to a recording paper placed on the thermal recording medium, to thereby record the information pattern on the recording paper.
A conventional heat-transfer recording medium which permits recording in two colors by utilizing differences in heating temperature is shown in FIG. 1. Referring to FIG. 1, the heat-transfer recording medium comprises a substrate 1, a first solid heat-sensitive ink layer 2 on the substrate, and a second solid heat-sensitive ink layer 3 on the first solid heat-sensitive ink layer 2. The first solid heat-sensitive ink layer 2 melts upon heating to a temperature of T.sub.1 .degree.C. Similarly, upon heating to a temperature of T.sub.2 .degree.C., which is lower than T.sub.1 .degree.C. (T.sub.2 &lt;T.sub.1), the second solid heat-sensitive ink layer 3 melts.
A heat means, e.g., a thermal head, is used to control the heat energy to be supplied to the recording medium. When the recording medium is heated to a temperature which is lower than T.sub.1 .degree.C. but higher than T.sub.2 .degree.C., the second solid heat-sensitive ink layer 3 alone melts. If the second solid heat-sensitive ink layer 3 contains red pigment or dye, recording will be performed in red on the recording paper. When the recording medium is heated to a temperature which is higher than T.sub.1 .degree.C., both ink layers 2 and 3 melt. If the first solid heat-sensitive ink layer 2 contains black pigment or dye, the red and black pigments or dyes will intermix, achieving recording in a black recording color.
The conventional heat-transfer recording medium, however, suffers from a difficulty in that the desired recording color cannot be obtained unless the inks in the two layers are fully mixed, since the solid inks having the different colors are provided in a layered configuration. Therefore, the conventional recording apparatus is designed so that sufficiently great energy can be supplied in order to fully intermix the inks in the two layers. This is one of the factors which inhibits both the miniaturization of the apparatus and high-speed recording.